PubMed · 6864102
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M J Meyers. 1983. Information processing and the Slingerland Screening Tests.. https://doi.org/10.1177/002221948301600303
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In this study, the equilibrium-point hypothesis of muscle-torque generation is used to evaluate the changes in central control parameters in the process of postural-maintenance learning. Muscle torque is described by a linear spring equation with modifiable stiffness, viscosity, and equilibrium angle. The stiffness is considered to be the estimation of the central command for antagonist-muscle coactivation and the equilibrium angle to be the estimation of the reciprocal command for a shift of invariant characteristics of the joint. In the experiments, a load applied to the forearm was released. The subjects were instructed to maintain their forearm in the initial horizontal position. Five sessions of approximately twenty trials each were carried out by eight subjects. During two "control" series, the load release was triggered by the experimenter. During three "learning" series, the load supported by one forearm was released by the subject's other hand. The elbow-joint angle, the angular acceleration, and the external load on the postural forearm were recorded. These recordings as well as anthropometric forearm characteristics were used to calculate the elbow-joint torque (which we called "experimental"). Linear regression analysis was performed to evaluate the equilibrium angle, joint stiffness, and viscosity at each trial. The "theoretical" torque was calculated using a linear spring equation with the found parameters. The good agreement observed between experimental and theoretical joint-torque time courses, apart from the very early period following unloading, argues in favor of the idea that the movement was mainly performed under a constant central command presetting the joint stiffness and the equilibrium angle. An overall increase in the stiffness occurred simultaneously with a decrease in the equilibrium angle during the "learning" series in all the subjects. This suggests that subjects learn to compensate for the disturbing effects of unloading by increasing the joint stiffness. The mechanism possibly responsible for the presetting of the central control parameters is discussed.
BACKGROUND: Animal studies suggest that vasopressin has cognitive-enhancing properties and oxytocin may have amnestic effects. A clinical report suggests that the acute increase in oxytocin-associated neurophysin predicts clinical response to electroconvulsive therapy (ECT) in depressed patients. METHODS: Medication-free patients with major depression were randomized to receive right unilateral or bilateral ECT administered with electrical stimulus intensity at either just above seizure threshold or at 150% above seizure threshold. The associations between plasma vasopressin, oxytocin, ECT treatment parameters, clinical outcome, and cognitive effects were assessed. RESULTS: The sample comprised 55 patients. At the second ECT, patients receiving ECT at 150% above initial seizure threshold had significantly greater increases in plasma vasopressin than patients receiving low-dose ECT (ps < .01-.04), with no effects of electrode placement. At the second and ninth ECT treatments, the vasopressin or oxytocin surges were not associated with clinical improvement, seizure duration, time to orientation, or memory test performance. There were inverse trend-level associations between the acute surge in oxytocin levels at the ninth ECT and clinical response, contradicting a report in the literature. CONCLUSIONS: Overall, these findings do not support the hypothesis that diencephalic seizure propagation is central to the mechanism of action of ECT.
There has been a good deal of controversy over whether attention influences area V1-the first cortical area onto which information from the retina is projected. Attention to motion has been found to modulate monkey area MT and the human homolog of MT/MST. Here we show that activation of V1 by attention to motion is task dependent. Our stimulus consisted of a group of translating random dots superimposed over another group of random dots executing expansion motion. Subjects were instructed to pay attention selectively to the translation, expansion, or neither in particular (passive condition). The activity in the human MT/MST homolog measured by functional magnetic resonance imaging (fMRI) was significantly higher in both the translation and the expansion conditions than in the passive condition, while the activity in area V1 was significantly higher only in the translation condition. These results show that attention to motion modulates area V1, and more interestingly that high-level cognitive processing such as attention may directly or indirectly determine the retroactive extent of feedback within the motion pathway in a manner dependent on the type of motion attended.